69

Hello Chris, referring the 1998 schematics I sent you showing the voltage tables, I note the following;
At the fuel tanks yellow PED connector;
PIN “A” 5 Volts
PIN “D” Ground
The PCM send 5 volts to PIN “A” yellow PED connector and these 5 volts are adjusted as follows depending on fuel level to flow back to the PCM via PIN “C” on the yellow PED connector on fuel level assy .
Fuel Level Conversion Table
Approximate Values
The voltages in the Fuel Level Conversion Table are approximate values.
Fuel Level Left Tank voltage Right Tank Voltage
100 % 2.5 V 2.5 V
75 % 2.5 V 1.5 V
50 % 2.5 V Less than 1.0 V
25 % 1.7 V Less than 1.0 V
0 % Less than 1.0 V Less than 1.0 V
The “adjusted” voltage is sent back to the PCM via PIN “C”.

Fuel level sensor check using a multi-meter
NOTE do this check on your OLD and NEW level sensor and post your findings.
Remove the right tank fuel level sensor. Connect the DMM between the
fuel level sensor signal circuit and the fuel level sensor ground circuit
(sensor side). Set the DMM to the 400ohms range. Sweep the fuel level sensor from
stop to stop. Expected values= 40ohms (±1ohms) to 250ohms (±2.4ohms)



If I was there helping you, my troubleshooting approach would be as follows as you have two codes.
DTC P0461 Fuel Level Sensor Performance
The left Fuel Level sensor, mounted in the rear side of the left fuel tank, measures fuel level
changes within the left fuel tank. The Left Fuel Level Sensor changes resistance based on fuel level. The Fuel Level Sensor has a signal circuit and a ground circuit. The PCM applies a voltage (about 5.0 volts) on the signal circuit to the sensor. The PCM monitors the changes in this voltage caused by changes in the resistance of the sensor in order to determine fuel level. When the fuel tank is full, the sensor resistance is high, and the PCMs signal voltage is only pulled down a small amount through the sensor to ground. Therefore, the PCM will sense a high signal voltage (fuel tank full). When the fuel tank is empty, the sensor resistance is low, and the signal voltage is pulled down a greater amount. This causes the PCM to sense a low signal voltage (fuel tank empty).



Conditions for Setting the DTC

Action Taken When the DTC Sets
• The Primary fuel tank is not full.
• More than 241 km (150 miles) have been accumulated.
• The PCM does not detect that the fuel level in the left fuel tank moved by at least 4.0 liters(1.1 gallons).
<OR>
• The Primary fuel tank is full.
• The Secondary fuel tank is near empty
• The fuel level in both fuel tanks does not change after traveling more than 241 km
(150 miles). Observe, if the secondary fuel tank is empty, the primary fuel level should
decrease after 241 km (150 miles).

>Possible fuel transfer from the right tank to the left fuel tank issue<

The PCM uses inputs from the Fuel Level sensor 1 and the Fuel Level sensor 2 in order to calculate
the total fuel remaining in both fuel tanks. The system sends this information via the serial data to the IPC. This information displays on the fuel gauge.

>AND<

DTC P1432 Fuel Level Sensor 2 Circuit Low Voltage
The Fuel Level sensor 2, mounted in the rear side of the right fuel tank, measures fuel level
changes within the right fuel tank. The Fuel Level sensor 2 has a 5.0 volt reference circuit, a
ground, and a signal circuit. When the fuel level is low the sensor output voltage is high. When the fuel level is high the sensor output voltage is low.
The PCM uses inputs from the Fuel Level sensor 1 and the Fuel Level sensor 2 in order to calculate the total fuel remaining in both fuel tanks. The system sends this information via the serial data to the BCM. This information displays on the fuel gauge.

Conditions for Setting the DTCP1432
• The Fuel Level sensor voltage is below 0.39 volts.
• The above condition present for greater than 50 seconds.



1.Disconnect the PCM connector inspect for corrosion on the wire pins etc.
2.Disconnect electrical connectors from the LEFT and RIGHT fuel tank sending units inspect for corrosion on the wire pins etc.
3. Now that the wire harness is isolated from the PCM and the LEFT and RIGHT fuel tank sending units, perform checks on the wire PINs to determine if there are “OPENS” “SHORTS” and “GOUNDS” as per the wire schematic.
4. IF a discrepancy is noted on the wire check, please post your findings.
5. IF no discrepancy is noted, make sure the car battery is fully charged, clean connector pins with an electrical contact cleaner and re-connect the PCM and perform the 5 Volt checks to determine the PCM is sending the 5 volts to the LEFT and RIGHT fuel tanks.
6. IF a discrepancy is noted on the wire check, please post your findings.
7. IF no discrepancy is noted, make sure your OLD right tank fuel sender assy, specifically your jet pump is clean as debris in this jet pump MAY have contributed to the DTC P0461 as the fuel was not transferring from the right fuel tank to the left fuel tank. After ensuring the jet pump is clean, install in tank,
8. Reconnect wire connectors to the LEFT and RIGHT fuel tanks.
9. Clear all DTC codes, if you cannot clear the codes, post your code findings. If the codes clear, please post fuel gage reading and estimate how many gallons you have in the tank (total gallons) as this will make a difference as to which tank LEFT and RIGHT will have fuel in it.

I hope that my post will get you a step closer to solving this issue.
Kevin

Chris Arnold

I noticed that too, but the 1997 schematics differ from the 1998 schematics. Above the PCM part of pin "C", it also shows 5v. Do you feel the 1998 schematics are more correct? Am I misreading the meaning of that?

Part of the problem is that I cannot determine how to correctly wire the 2-wire replacement sensor, or exactly how to test it. I tried testing numerous configurations. Connected the 5v to the blue wire and tested both other posts on the fuel sender. I think I got 5v out of them regardless of the sender's position. Connected the 5v to the grey wire, and tested both other terminals by running one of them to to B and testing the opposite post, and the same one to C and testing the opposite post again. Then I did the same tests after connecting running the other post to B and C again for 2 more tests. In some cases I saw a spread from around 30mV to 90mV tested one way, and in another way I got as much at 190mV. Still, that's no where near the 2.5V it seems that I should be seeing. However, with these tests, at least I was able to measure a variable voltage output that corresponded to the changing inputs on the fuel sensor.

I initially replaced the sensor over a year ago, and the old sensor broke as I removed it, and I unfortunately threw it away. I figured if I screwed the pooch on the installation, I'd just take it to someone who knew what to do. Unfortunately, no one I've found in Germany has the slightest idea how to work on this

This test worked just fine on both of the 2-wire sensors I have. It doesn't matter which way I connect the DMM to the 2 wires. It was almost exactly 40 and almost exactly 250.



Kevin, thanks again man. I will go down this checklist tomorrow afternoon (Germany time = EST+6 hours). I don't think I'm having trouble with fuel transferring to the left tank. It looks like 461 will set when I've traveled more than 241km (150 miles) when the right tank is low, as it always is, and the left tank hasn't moved. There's probably around 8-9 gallons in the right tank alone. Even if I only got 20mpg, it would allow me to go far enough to trip the 461 code. Also, I've always used my trip meter and average fuel economy from the DIC to calculate how much fuel I have left, and I know I can push the car upwards of 18 gallons worth of fuel without running out. Just an observation.... If I get far enough along without finding anything, I'll pull the jet pump for a look.

Chris Arnold

Here's what the extra post on the fuel sender looks like:

The third post can be seen above the posts that the blue and grey wires are attached to on the sender. In the old sender, I think this is where the 3rd wire went. In both of the replacement senders I have now, there is no third wire:

69

Hello Chris,
Regarding the 461 code, this is not “a normal condition” and will need to be addressed. As the engine consumes fuel from the LEFT Fuel tank, the RIGHT fuel tank will supply fuel to the LEFT fuel tank to keep the LEFT fuel tank Full until such time the right fuel tank has no fuel (empty). Reference the fuel level voltage tables showing the various fuel tank levels and voltages.
After you posted a pic of the fuel sender card, I got to looking at it carefully and noted the 2 wire configuration as you stated and your reference to the “3rd” wire on your OLD sensor in previous post.
Comparing the 1997 fuel schematic and your fuel sender card pic showing only 2 wires, I get the impression that when you replace this sensor two years ago, the fuel gage did not work at all or was a “Dead Needle” on your dash gas gauge.
Am I correct regarding the “Dead Needle” on your dash gas gauge after you replaced this sensor two years ago?

Chris Arnold

Not exactly, Kevin. I can reset the codes in the DIC and for a brief time, a minute or so, the gauge will show about 3/8 of a tank when the tank is above 1/2 full. After that minute the code sets, the DIC reads "low fuel," and the gauge goes "dead." Each time I reset the code, which I have to turn the car off to do, the gauge will return to a level that is consistent with the amount of fuel in the left (drivers) tank. In this way, I can check to make sure I actually have fuel in the car. This is why I'm sure that the left tank sending unit is working fine.

Before the initial replacement of the right-side fuel sender, the gas gauge was intermittent. It often went to empty, but it also went to full occasionally. I assumed that the sending unit was corroded due to the sulfur in the gas like many other corvette guys have discussed. I didn't want to mess around with seafoam and additives. So, I thought I'd just replace the sending unit and be done with it. Little did I know....

Critically, a difference I seem to recall is that before I replaced the original sender the gas gauge, though intermittent, would sometimes show full. It never does this now. Now, it maxes at 3/8 of a tank, but even then it won't maintain this level when the code is set. The fact that I can drive a considerable ways and still note 3/8s of a tank when I reset the gauge leads me to believe that the siphon is working without issue. Additionally, I have no problem going the range one would expect on a full tank.

69

Hello Chris, the gauge issue you describe makes sense as the LEFT fuel tank level sensor is NOT getting the voltage from the RIGHT fuel tank level sensor.
Missing 3rd wire which will allow the voltage to flow from pin “B” on the RIGHT fuel tank sender to pin “B” on the LEFT fuel tank sender.

Chris Arnold

I believe I've solved the issue. The simple fact of the matter is that all 3 wires are necessary. I got some long single wires and connected everything up while I sat in the car. Terminal A from the wiring harness goes to the unwired post on the sending unit. Terminal B goes to grey wire, Terminal C does indeed go to the blue wire. Moving the float arm position resulted in getting almost a full tank (right under the F) to about 5/8s of a tank. This is the first time I was able to get the gauge to react in a way that makes sense, even though it didn't use the complete sweep of the gauge itself.

I can't explain the voltages, though. Perhaps, it's just my ignorance in testing circuits. I performed the test by first grounding the DMM to the frame. I used terminal D, which I know to be a good ground having tested the voltage across from A to D. With Terminal D, I first connected the blu wire grounding it. I connected Terminal A (5V) to the unwired post. Then, I hooked the red lead from the DMM to the grey wire and tested the voltage through the range from a low fuel position to a high fuel position on the sender. From the grey wire, I got 18.5mV at low and 25.3mV at high.

I then performed the same test, except I grounded the grey wire to Terminal D and tested the blue wire. I got 1.64V at low, and 4.28V at high.

I expected less then 1V at low, and around 2.5V at high, because of the data you sent me. Frankly though, that data is not clear to me, because I'm not sure how the computer reads the data. For all I know, the PCM or BCM may have an additional resistor or some other electrical voodoo may be going on wherever it takes its reading.

Anyway, I think the path forward is clear. I need to get a soldering iron and the correct connector and wire the 3rd currently unwired post on the sender, and give reinstallation another shot. I'll go to the local german hardware store tomorrow and see if I can find a soldering specialist or at least a good soldering iron. I've never soldered electronics, and aside from playing around with my father's as a kid, I don't have any experience with it. But, at this point I'm ready to give it my best college try, and it doesn't look that difficult. I've just gotta be careful to keep the solder where it's supposed to go and not let it short to any other terminal.

Chris Arnold

Some luck today: I was able to pull the correct connector for the 3rd wire to the fuel sensor from a '90s model Opel Corsa wiring harness connector in the engine bay. Opel is a GM brand. I'm not sure if these connectors are relatively common, but if you can't get one at an electrical shop, you can get one out of another GM car, most likely. I saw a couple of numbers stamped on the connector. "17" is stamped at the end of the connector that goes to the wire, and "P12" on the end that will go inside of the black connector. Hopefully, this is helpful to anyone following in my footsteps.

On the bright side of this ordeal, if soldering the wire and installing this sending unit works out, this is not only an $80-ish (GM parts direct - http://www.gmpartsdirect.com/results...umber=10333749) fix instead of replacing the entire assembly for $300+.

69

Hello Chris, great to hear you made some progress!
I wonder if instead of soldering on a 3rd wire to the fuel sender card and running it to the pin location on the BLACK PED connector, if you were to use a small “jumper wire” on the back side of the BLACK PED connector to simulate that 3rd wire from fuel sender card.
The reason I’m thinking this is that the Fuel level sender assembly part number is the same for a 1997 and a 1999 which utilize (1997 3 wires and 1999 2 wires) therefore there is some “magic” done to this part number to be able to install this part number in both model years

#01-06-04-022: Inaccurate/Erratic Fuel Level Gage Readings (Install New Sensor, Strainer and/or RH Fuel Sender Assembly) - (Mar 16, 2001)
Parts Information
Part Number
Description

88896043
R.H. Fuel Sender Kit (1997-1999 M.Y.)


Kevin

Chris Arnold

Kevin, I don't think I understand. What does the wire jump to and from? If it's wired the way I did earlier when I got a seemingly successful test from the fuel gauge, then I don't see how adding a jumper wire would work. The test required me to send the power from A to the unwired connector. The black PED connector only holds the pins from the wires in place and snaps into the orange connector. Without the wires from the fuel sender, the black PED connector is nothing but plastic.

I agree with you though that something is going on with the '99 to be able to pull it off with 2 wires, but I don't have a clue what it is.

69

Hello Chris, after further research, my jumper wire theory will not work as confirmed by this Chevrolet Corvette Right Fuel Pump Assembly OEM ACDelco P/N 89047746 which is only compatible with Model years 1997 thru 1999.
Note this 89047746 has the 3 wire configuration from the sender card, (Yellow. Gray Lt Blue wires).
Kevin

Chris Arnold

Didn't work. Taking a break for a while... so pissed

69

Hello Chris, I understand your frustration and I have been trying to wrap my mind around this problem also. I have had great success helping owners of 1999 and above troubleshoot their fuel systems, but for the model year 1997 and 1998 this problem was a “learning experience” for me.
I have come to the impression that the 2 wire sensor that can be installed in the LEFT fuel tank CANNOT be used in the RIGHT fuel tank due to the voltage needing to pass through the RIGHT fuel level sensor to the LEFT fuel level sensor, (missing 3rd wire).
Using a previous Forum Post that had a photo of the 3 wire sensor, you can see electrical path. The “red box” on the 3 wire sensor appears to be a resistor on the schematic. The 2 wire sensor does not have this resister in the electrical path. I believe this is the reason why you were not getting the voltage values in the 1998 table.



Forum Thread Acknowledgements
FirethornC5 Did GM omit strainers on the RH sender?
http://forums.corvetteforum.com/c5-t...rh-sender.html
blu00rdstr New Vs. Old Fuel Level Sensors
http://forums.corvetteforum.com/c5-t...nder-pics.html

Based on your struggles to get this 2 wire sensor to work correctly in the RIGHT fuel tank in your 1997 Corvette,> the wire schematics> and AC Delco only supplying the 2 Wire sensor to the public which is only applicable to the LEFT fuel tank (as per AC Delco), I believe that you may have received some bad information as to the LEFT 2 Wire sensor being able to be installed in the RIGHT fuel tank 3 wire sensor position and be fully operational for a model year 1997 and 1998 Corvette
.
Posting to members or vendors

If any forum member or vendor viewing this thread has different information, please post up as WE have a CF member in Germany needing assistance to make us proud running his C5 up and down the Autobahn with a fully functional fuel gauge!
Kevin

Chris Arnold

LOL.

Part of me wants to take the straightforward route of just ordering the right part now. The other part, after struggling with this problem for over a year makes me want to keep trying to fit this square peg through the triangular hole. So, next question:

Is it possible to identify the resistance needed and order an in-line resistor to place on the output wire? That could be done inside or outside of the tank. Seems like a resistor would be cheap. Is trial an error the only solution? Wonder if AC Delco has any electrical techs willing to discuss this.

Chris Arnold

Well, I pulled the sender from the passenger tank and it looked identical to the correct one with three wires, though this one only had two, it also had the resistor-looking thing on the unwired post. Tried replacing the passger sender with one of the new ones. No issues. After installation, the fuel gauge works up to just under 1/2 tank like it did before. I was feeling pretty good about the fact that the resistor looked right. Unfortunately, when I hooked it all up, it failed to properly function, too. One time, the vette's gauge inexplicably jumped to Full...Couldn't tell you why. It stayed there for a while, and I tried turning the key off and on several times before it reset, but I couldn't get it to repeat that.

I finally caved and bought the assembly. It's on the way. Somehow I feel it won't work too. I found an unconfirmed PCM pin-out diagram, and intend to do some continuity tests tomorrow.

Chris Arnold

Finally got the right pins from the PCM to B and C on the wiring harness. They have good continuity after all. I think I can logically deduce that terminal A is good since I'm getting the 5V signal and that D is also good since I used that as my ground to check the 5V signal from A.

Chris Arnold

Cheapest place to buy the correct assembly was Amazon for $214 shipped.

Chris Arnold

Success! It's amazing how much more installing the correct part can do.

69

Great news Chris

Moderators, please consider pining this thread for the 1997/1998 corvette owners.
Kevin

Chris Arnold

I measured the additional resistor for the 3rd wire at 243 ohms. I'm guessing it's probably a 250 ohm resistor and my multimeter isn't perfect.

Perhaps if someone wants to try using the left side sending unit all they would have to do is solder a wire with an in-line resistor of 250 ohms onto the 3rd wireless post. I suspect this would be doable and should save about $120. It's just a guess, though.